Article

라거맥주 효모 침전물의 유변학 및 형태학적 변화

이준호1, 이신영1, 허원1,*
Lee Joon Ho1, Lee Shin Young1, Hur Won1,*
Author Information & Copyright
1강원대학교 공과대학 생물공학과
1Department of Bioengineering and Technology, Kangwon National University
*Corresponding author: Hur Won, Department of Bioengineering and Technology, Kangwon National University, Chuncheon 200-701, Korea, Tel: +82-33-250-6276; Fax: +82-33-243-6350, E-mail: wonhur@kangwon.ac.kr

ⓒ Copyright 2013 Korean Society for Food Engineering. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Jul 05, 2013; Revised: Sep 06, 2013; Accepted: Sep 25, 2013

Published Online: Nov 30, 2013

Abatract

Yeast sediment is used for pitching subsequent batches or for making yeast extract in lager beer fermentation. The rheological properties of dense yeast sediments and those stored at different temperatures and periods were investigated using a rotational viscometer. A dense suspension of yeast cells harvested at the stationary phase showed slight dilatancy (n = 1.19-1.25). The dilatant yeast suspension became more viscous after several days at room temperature as well as at 4°C. A high shear rate (170.7 s-1) reduced shear thickening in the yeast suspension stored at room temperature for 2 and 4 d. However, dilatancy was restored and even increased in the yeast cells at 6 d. Flow cytometry showed that haploid, diploid, triploid, and tetraploid yeast cells are present in the stationary phase yeast cells, in which polyploid populations varied dynamically. Image analysis of SEM micrographs revealed that the yeast cells have a bimodal distribution in size and the distribution varied significantly in yeast sediment stored at room temperature. Thus, the results suggest that the rheological properties of yeast sediments related to morphological changes could be associated with polyploid populations. Accordingly, rotational viscometry can be applied to monitor the physiological status of yeast sediments in the stationary phase.

Keywords: lager yeast; yeast sediment; yeast rheology; yeast polyploidity